16. May san

a. Cong dung va phan loai

* Cong dung:

May san chu yeu dung san nen mong cong trinh, nen duong, nen san bay, ngoai ra no con lam cac cong viec: xoi dat, tham gia dao, dap nhu may ui (nhung yeu hon), bao co cay, dao ranh thoat nuoc hai ben le duong, bat ta-luy, san rai tron cap phoi da dam, soi, cat...

Doi tuong nen ma may co the thi cong la dat thuoc cap IIII nhung chu yeu la cap I va cap II. Cu li san dat co hieu qua 500 m.

* Phan loai:

+ Dua vao kha nang di chuyen: May san khong tu hanh; May san tu hanh (do co nhieu nhuoc diem ngay nay khong con duoc su dung nua).

+ Theo phuong phap dieu khien thiet bi cong: Loai dieu khien co khi, loai dieu khien thuy luc.

+ Theo cong suat va trong luong may san duoc chia thanh cac loai: Nhe (trong luong: 7-9 tan, cs dong co: 50-63ml); Trung binh (trong luong: 10-13 tan, cs dong co: 65-100ml); Nang (trong luong: 13-19 tan, cs dong co: 130-160ml); Rat nang (trong luong: >19 tan, cs dong co: >160ml);

b. Cau tao va nguyen ly lam viec cua may san:

* Cau tao:

Hinh 4-18. So do cau tao may san

a. Tong the may san; b. So do co cau quay luoi san; c. Co cau dao banh truoc;1. Dau may; 2. Khung chinh; 3. Luoi san; 4. Co cau dieu chinh; 5. Khung keo; 6. Mam quay; 7. Xi lanh nang ha luoi san; 8. Dong co thuy luc; 9. Khung may; 10. Xi lanh dao banh truoc; 11. Banh truoc; 12. Cau truoc; 13. Khop van nang.

Cau tao chung cua may san duoc the hien tren hinh 4.18 voi nhung dac diem co ban sau: dau may va buong dong luc dat o phia sau, may duoc trang bi bo di chuyen banh hoi, hai truc phia sau nhan dong luc tu dong co thong qua bo truyen co khi hay thuy luc trung gian, hai banh truoc lam nhiem vu dan huong co cau lai, co cau dao banh cho phep nghieng banh voi mat nen tao dieu kien cho may san lam viec on dinh ngay ca tren suon doc ngang. Dau may phia sau va he thong banh lai phia truoc duoc lien ket voi nhau bang khung chinh 2, tren do ga lap bo cong tac cua may cung voi he thong dieu khien.

Bo phan chinh cua thiet bi cong tac la luoi san 3, luoi san duoc bo tri duoi mam quay 6 va khung keo 5 tai ba diem va vi the luoi san lam viec linh hoat hon luoi ui.

Co the dieu chinh duoc goc dao cua luoi san bang tay (quay luoi san mot goc  xoay quanh truc dung cua may).

* Nguyen ly lam viec:

Khi can cho may san cat dat, dieu khien quay luoi san de co mot goc  dinh truoc va ha luoi bap vao nen de co mot chieu day vo bao thich hop. Sau do cho may tien ve phia truoc, dat duoc cat se chay doc luoi va do ra phia ngoai may.

De san rai vat lieu chi can nang luoi san len theo chieu day muon rai va tiep tuc cho may tien. Cac cong viec tao dang mat nen hay bat taluy, dao ranh thoat nuoc ... deu co the tien hanh duoc nho phoi hop cac thao tac dieu khien luoi san nhu da mo ta o tren.

Khi may san lam viec can phai giu may chay theo mot duong thang. Chu y khong de banh xe cua may san di tren truc dat xoi do ra trong hanh trinh truoc vi dat roi vao banh xe se can tro dieu khien va lam may kem on dinh.

Trong qua trinh thi cong dao dap bang may san nen ke tiep nhau lam viec ca hai mep cuoi cua luoi san nhu vay luoi cat se mon deu va nang cao chat luong cong trinh.

c. nang suat cua may san

+ Tinh nang suat cua may san:

Nang suat su dung cua may san cao hay thap la tuy thuoc vao trinh do nguoi dieu khien. Dieu nay duoc the hien qua viec xu ly cac thao tac cua may san phu hop voi dieu kien dia hinh, loai dat va toc do lam viec cua may. Vi du: khi cat dat may san nen di so I, II; khi van chuyen dat di so III, IV. Cung nhu may ui, khi lam nhiem vu dao va van chuyen dat khong nen cho may san van chuyen dat o cu ly xa qua (nen duoi 100 met).

Nang suat cua may san khi dao va van chuyen dat duoc tinh theo cong thuc:

m3/ca

Trong do: V- The tich khoi dat truoc luoi san, (m3);

T- Thoi gian lam viec trong mot ca (gio);

ktg- He so su dung thoi gian (ktg = 0,80,95);

Tck- Thoi gian mot chu ky lam viec (gio);

kx- He so toi xop cua dat (nhu cua may ui).

Trong truong hop san phang, nang suat may san duoc tinh nhu doi voi may ui van nang.